This invention relates to catheters, cannulae, endoscopes and similar flexible probe devices. These devices are typically passed into and through a body orifice, incision, artery, vein or other passage until they have reached a desired position within the body. Probe devices of this kind often include fiber optic bundles for illumination and/or viewing purposes, and, depending on the particular device, feed lines for air or other fluid, and channels for suction, forceps, and the like. See, for example, U.S. Pat. No. 4,559,951.
Of great concern with such devices is their flexibility and steerability, characteristics which significantly bear on the ease with which the device can be introduced and passed through the various channels of the human, or animal body.
Various attempts have been made to produce a catheter, cannulae, endoscope or the like which is readily insertable and manipulatable for ease of advancement through body cavities or channels. See, for example, U.S. Pat. No. 4,543,090 which discloses a catheter having a distal end for ready insertion into a body, with a plurality of temperature-activated memory elements in its distal end. Each memory element assumes a first shape in response to temperature and a second shape in response to a force. The memory elements are coupled together and to a control means for deflecting the distal end of the catheter in a plurality of directions to steer or aim it within the body.
In U.S. Pat. No. 4,176,662 an endoscope is disclosed which includes a propulsion system consisting of two radially expandable bladders separated by an axially expandable bellows. In this device, only the forward bladder is attached to the distal end of the endoscope so that by expanding and contracting the bladders in proper sequence, propulsion of the endoscope is achieved.
U.S. Pat. No. 3,890,977 discloses a biological catheter or cannulae which incorporates material such as a titanium-nickel alloy having a heat activated shape memory. The device is formed and annealed at high temperature into a shape for effective anchoring or proper location in an organ or other structure of the body. At a temperature below its transitional temperature, it is reformed into a shape for ease of insertion, and when located as desired, it is heated above its transitional temperature to assume its proper anchoring or locating shape.
The catheter disclosed in U.S. Pat. No. 3,773,034 bends the distal end of a catheter as desired, utilizing a fluid.
The catheter disclosed in U.S. Pat. No. 3,674,014 includes permanent magnets and a magnetic field to bend the distal end of a catheter.
U.S. Pat. No. 3,605,725 utilizes mechanically manipulatable control reins to steer a catheter, while U.S. Pat. No. 3,043,309 discloses electromagnetic means for directing a tube in an intestinal intubation procedure.
Other prior art patents relevant to the use of heat activated shape memory alloy metals in medical devices include U.S. Pat. Nos. 4,556,050 and 4,411,655.
The principal object of this invention is to utilize shape memory metal technology to provide a steerable catheter, cannulae, electrode, endoscope and the like for easy insertion and advancement within the body.
To this end, the invention in its broader aspects, and in accordance with one exemplary embodiment, includes an elongated, flexible tubular body of multi-layered wall construction having proximal and distal ends; a plurality of sets of electrical conductors integrally contained within the multi-layered wall construction; at least one pair of relatively rigid rings encircling and fixedly attached to the tubular body at axially spaced locations therealong; a plurality of temperature activated shape memory wires extending between the rings and electrically connected to and, a power source through the conductors; a power source operatively connected to the conductors, along with an associated control device for selectively heating individual memory wires to a predetermined temperature to cause such wires to contract and thereby effect a bend in the distal end of a catheter as it progresses within the body.
More specifically, the elongated, flexible tubular body is preferably of multi-layer construction including an inner tubular member of relatively stiff plastic material which may enclose fiber optic bundles, air feed channels, electrodes and the like. A flat ribbon-type conductor is spirally wrapped about the inner tubular member and covered with insultaing material.
Fixed attached to an outer surface of the insulating material at axially spaced locations in the distal end area of the tubular member are a plurality of rigid rings, preferably made of aluminum or plastic material. These rings may be fixed to the outer insulating surface by an suitable adhesives, such as known epoxy resins.
Individual titanium-nickel shape memory alloy wires extend between, and are attached to adjacent rings, each pair of rings defining a segment along the length of the catheter-like flexible probe. Each segment preferably has four titanium-nickel alloy wires, spaced 90.degree. apart about the periphery of the probe and extending axially along the probe. The individual wires are electrically connected through the rigid ring to appropriate ones of the conductors beneath the insulating layer of laser welding or other suitable methods including mechanical crimping.
The conductors are connected at the proximal end of the tubular probe to a suitable control device, such as a microprocessor, which is operable to selectively heat various of the tittanium-nickel alloy wires to a predetermined temperature which causes that wire to contract, i.e., shorten its length so as to bend the distal end of the probe in the desired direction.
By sequentially heating selected ones of said wires, it is possible to steer the probe to the desired location within the body.
Further objects and advantages of the invention will become apparent upon consideration of the drawings, detailed description and claims which follow.